Re: [SI-LIST] : Bulk Caps -> Inductor? -> Plane

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From: Yu Wang (wangy_km@yahoo.com)
Date: Thu Apr 13 2000 - 08:15:58 PDT


Matt,
As other guys mentioned, if add some bulk caps on the
VCC plane side of L202, it should be ok, at least it
will not be a trouble maker. What I am going to
suggest here is you should pay attention to the
shut-down bounce raised by L202. It may damage your IC
and I met this problem 3 years ago. Fortunately, it's
not difficult to deal with. What I did was just add a
diode to provide a bypass to the inductor to clamp the
voltage spike.

Yu Wang

--- mjs <mjs@enteract.com> wrote:
>
> I am not sure if the list accepts attachments, but
> here goes.
> If the attachment is stripped by the listserve,
> please find
> it visible at www.enteract.com/~mjs/induct.gif (16k)
> --
>
> The attached gif show a snip from a schematic
> currently in layout.
>
> The transformer shows the secondary of the SMPS,
> connected
> to a whole mess of bulk capacitance, especially on
> +5V net.
>
> Please note L202 series inductor inserted between
> the bulk capacitance and
> the connection to the power plane. This worries me
> most. There seems to
> be no valid reason to stuff series inductance
> between the bulk and the
> plane. Further, all the local ceramic IC pin bypass
> will also have to
> suck current through that same inductor. Seems like
> a terrible idea to
> me. Comments welcome.
>
> Matt Stanik
> Sr. PCB Design Eng.
> Charles Industries, Ltd.
>

> ATTACHMENT part 2 image/gif name=induct.gif

=====
Yu Wang, Ph.D
U.T. MD Anderson Cancer Center
1100 Holcombe Blvd., Box 217
Houston, TX, 77030
Tel:713-745-1671

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